The present invention relates to amorphous Zr alloys which have a high glass-forming ability and excellent strength and toughness.
Amorphous metal materials having various forms, such as thin ribbons, filaments, particles and the like, can be obtained by rapidly cooling molten alloys. A thin-ribbon-shaped amorphous alloy is easily manufactured by means of a single roll method, a twin-roller method, an in-rotating water melt spinning method and the like, in which a large cooling speed can be obtained. Conventionally, various amorphous alloys have been provided using alloys of Fe, Ni, Co, Pd, Cu, Zr or Ti; those amorphous alloys show properties unique to amorphous alloys such as high corrosion resistance, high strength, and the like. Especially, an amorphous Zr alloy is expected to be applied to the fields of structural materials, medical materials and chemical materials as a new kind of amorphous alloy having an outstanding high glass-forming ability compared to other amorphous alloys.
However, shapes of the amorphous alloys manufactured by means of previously mentioned methods are limited to thin ribbons or thin wires; it is difficult to process the amorphous alloys of those shapes into a form of final products. Therefore, the uses of such amorphous alloys are limited in industry.
On the other hand, it is known that when amorphous alloys are heated, some of alloys
On the other hand, it is known that when amorphous alloys are heated, some of alloys undergo transition to a phase of supercooled liquid before crystallization and indicate a decline in viscosity. For example, when heated at a speed of 40xc2x0 C. per minute, an amorphous Zr alloy is observed to remain in the supercooled liquid phase for a range of temperature of the maximum of 120xc2x0 C. before crystallization starts (see Mater. Trans., JIM, Vol. 32, (1991), 1005).
In the supercooled liquid phase, the low viscosity of the amorphous alloy allows one to form it into a given shape by closed squeeze casting process and the like; for example, gears can be formed of an amorphous alloy (see Nikkan Kogyo Shinbun, Nov. 12, 1992). Hence, amorphous alloys having a wide range of the supercooled liquid phase can be said to provide excellent workability. Among such amorphous alloys having a wide range of supercooled liquid phase, an amorphous Zrxe2x80x94Alxe2x80x94Nixe2x80x94Cu alloy has a range of temperature of 100xc2x0 C. as the supercooled liquid phase, therefore, is considered to be an amorphous alloy with excellent applicability, such as high corrosion resistance (see Japanese Examined Patent Application Publication H07-122120).
The glass-forming ability and a method for manufacturing of those amorphous alloys have been further improved. As a result, Japanese Laid-Open Patent Application Publication H08-74010 discloses development of an amorphous Zr alloy having a 100xc2x0 C. range for the supercooled liquid phase and a thickness exceeding 5 mm. Also, various manufacturing methods to improve mechanical characteristics of the amorphous alloys have been tried (Japanese Laid-Open Patent Application Publications: 2000-24771, 2000-26943, 2000-26944); however, these amorphous Zr alloys do not provide sufficient mechanical characteristics as structural materials.
The amorphous Zr alloy described previously has a high glass-forming ability and relatively good strength characteristics due to the range of the supercooled liquid phase above 100xc2x0 C. Nonetheless, attempts to improve its mechanical characteristics have been made only in the manufacturing method; attempts to improve the composition of alloys has not been made.
Intending to provide an amorphous Zr alloy material having improved strength and toughness without impairing a temperature range for the supercooled liquid phase and a size enabling application to industrial use, inventors of the present invention studied the above issues. They discovered the an amorphous Zr alloy having high strength and toughness as well as excellent glass-forming ability can be obtained by melting an alloy in which a given amount of M element (one or two or more elements selected from a group consisting of Ti, Nb and Pd) is added to a Zrxe2x80x94Alxe2x80x94Nixe2x80x94Cuxe2x80x94M alloy of a given composition, followed by rapid cooling for solidification.
In other words, the present invention intends to provide an amorphous Zr alloy which contains non-crystalline phase of 90% or higher by volume wherein the alloy has a composition expressed as Zrxe2x80x94Alaxe2x80x94Nibxe2x80x94Cuc13 Md (in this expression terms are defined as follows:
M: one or two or more elements selected from a group consisting of Ti, Nb and Pd;
a, b, c, and d: atomic % wherein:
5xe2x89xa6axe2x89xa610;
30xe2x89xa6b+cxe2x89xa650;
b/cxe2x89xa61/3;
0 less than dxe2x89xa67;
remainder: Zr and inevitable impurities).
Further, a xe2x80x9crange of the supercooled liquid phasexe2x80x9d is defined as a difference between a glass transition temperature, obtained by differential scanning thermogravimetry at a speed of heating of 40xc2x0 C. per minute, and a crystallization temperature. The xe2x80x9crange of the supercooled liquid phasexe2x80x9d indicates resistance to crystallization, that is, stability of glass-forming ability. The alloy of the present invention has a range of the supercooled liquid phase over 100xc2x0 C.